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You were merely doing a bit of Welding, Karen. Once the contact had been made, the melted / vaporised metal allowed a low voltage arc to bridge the gap. Scary! A modern rechargeable can give you loads of current and your bracelet was shorting out the contacts. You have probably damaged your battery, btw.When I was a lad, I had real fun with a thick wire coat hanger held across the terminals of an old car battery of my Dad's. Melted it a treat with a few hundred Amps.I suggest you may have had a shock - but it wasn't an electric shock, it was probably a burning sensation! It just felt like a shock. Our brains tell us - Sparks = Shocks.You should never wear jewelery / watches when working on high current supplies. You could burn your arm off!.
Yes, I concur with SC. I think it quite possible that the dangers of being burnt in this way were overlooked by the designers. There is a tendency to think low voltage is no danger and forget the high current capability can heat things up rather well. I note that air vents in most domestic electrical equipment tend to have a fine cloth mesh across them nowadays to avoid bracelets or necklaces dangling through the gaps.
I had a remote control go saggy like a Dali ...
Normally you won't get an electric shock from an 18 Volt battery because the human body is quite resistive, so not much current will flow through it. But put something with a low resistance (like a metal bracelet) across the terminals of a high discharge rate battery and a very large current flows. As a result, the bracelet heats up and starts to melt very quickly. This can can result in very serious burns.When working with any electric equipment (cars, computers, etc.) it is a very good idea to remove ALL metallic jewelery. Wedding rings and metal watch straps have led to many accidental amputations!Although car batteries only put out twelve volts, they can be lethal. If you accidentally drop a spanner between the terminals, it may actually weld to the terminals. All the energy in the battery will then be rapidly dissipated inside the battery. The acid in the battery will start to boil from the heat produced and the case will vent and may even explode, sending a shower of hot, highly corrosive sulphuric acid over everything and everyone near by.This is an old idea, but worth repeating: When you disconnect a car battery, ALWAYS disconnect the "earthy" terminal first (these days, that will most likely be the negative side.)If you are disconnecting the earthy side and you accidentally allow your spanner/wrench to contact the vehicle's body or chassis, no harm is done.If you are disconnecting the live/hot side (while the earthy side is still connected) and you accidentally allow your spanner/wrench to contact the vehicle's body or chassis, you have just applied a short circuit across the battery. Expect the spanner/wrench to get hot and, if you cannot break the circuit because the spanner/wrench has welded itself between the battery and the body/chassis, start running, and get everyone else out of the area before the battery explodes.
I was once told by a man with a large traction engine with an attached funfair ride - producing 100V and up to 600A across open terminals - that he dropped a large spanner across the terminals, and it heated up to red heat, melted and fell between them without really slowing down.I have a feeling that the designers of drill batteries didn't really have people wearing dangley metal jewellery in mind when they built it. They have tried to stop you shorting it by recessing the terminals in a hole, just your bracelet is ideally designed to get around the safety precautions.
You were very lucky that is all that happened, a friend of mine still has a very bad scar from a 21st birthday watch strap that shorted a truck 24v ( why get it scuffed and covered in grease and oil?).QuoteWow thats terrible and I am understanding more about why mechanics do not wear jewelry. That makes perfect sense to me now,, some before but I did not realize the extent of danger involved!
Wow thats terrible and I am understanding more about why mechanics do not wear jewelry. That makes perfect sense to me now,, some before but I did not realize the extent of danger involved!
Quote from: Edster on 13/08/2009 20:02:38 I had a remote control go saggy like a Dali ... [attachment=9458]http://en.wikipedia.org/wiki/The_Persistence_of_Memory
Yes, high current (even at low voltage) is quite dangerous because of the heat/welding you can get from short-circuits.While it doesn't seem so far-fetched that a car-battery can be dangerous, people used to relatively harmless alkaline batteries don't realise just how much energy (and how much current can be drawn from) domestic rechargeables.(You should also be careful with the innards of modern computers and their power supplies as these can often supply tens of amps, albeit at 3.3V or less.)Many consumer rechargeable battery packs these days have overcurrent protection built in, in the form of "PTC" (positive temperature coefficient) devices which go almost open-circuit when overloaded (and reset after a few 10s seconds). Others have an inbuilt transistor switch connected to an overload sensor. Such devices are extremely cheap ($0.20 or something).It is rather scary that a battery of the size you show in the photo does not appear to have such a safety-feature. In the UK (where we have a quite strict safety regime) you would probably have grounds to take the problem up with our Trading Standards body who are supposed to ensure that consumer goods are safe.